In recent years, an engine control system which makes a computer compute the amount of fuel injection and the ignition timing based on operating conditions and controls ignition mechanisms (e.g., igniters) and fuel injection mechanisms (e.g., injectors) so as to develop spark discharge at a spark plug of each cylinder is widely used in an automobile.
FIG. 16 shows a schematic circuit diagram of wiring of such an engine control system. In general, an engine intended for automobile use is multicylinder, of which each cylinder has an igniter 3, an injector 4, and other mechanisms. The igniters 3 and the injectors 4 are in parallel connection with a power supply 5 arranged to supply electric power to them via electric wires.
Because the igniters 3 are applied with high pulse voltage, noise is apt to be generated especially in the igniters 3. Therefore, a noise filter 50 is generally provided to the wiring between the igniters 3 and the power supply 5.
In addition, the igniters 3 and the injectors 4 are connected also to an engine control computer 6 (hereinafter, referred to as an ECU) arranged to control the ignition timing of each of the igniters 3 and the amount of fuel injection of each of the injectors 4 via electric wires.
The plurality of electric wires drawn from the igniters 3, the injectors 4, and other mechanisms, and a plurality of electric wires arranged to connect a variety of electronic or electrical devices mounted in an engine room of an automobile are tied in a bundle and are routed through the engine room in the state of a wiring harness. The tying and connection of the plurality of electric wires drawn from the igniters 3, the injectors 4, and other mechanisms are conventionally made in the following manner.
As shown in FIG. 17, sheaths at ends of a plurality of electric wires 100 are striped off, and the ends of the electric wires 100 are put together and welded by ultrasonic welding or resistance welding. Then, the welded end of the electric wires 100 is inserted into a cap 102 made of a resin, and a resin 104 such as an epoxy resin is injected in the cap 102 in order to waterproof the ends of the electric wires 100.
A connection between the electric wires thus tie and connected and the noise filter provided in the engine room is made by routing the electric wires to the noise filter.
In addition, a connection of the electric wires to a ground such a car body is made by routing the electric wires to the ground. This connection work is to be made for each bundle of the electric wires.
As a prior art literature relating to the present invention, Japanese Patent Application Unexamined Publication No. 2004-192991, Japanese Patent Application Unexamined Publication No. 2004-179032, and Japanese Patent Application Unexamined Publication No. Hei11-40281 are cited.